In recent years, attempts have been made to improve the efficiency of hot mix asphalt (HMA) plants. Conventional direct-fired prior art drum hot mix asphalt plants often utilize a mixture of virgin aggregate material and recycled asphalt products (RAP). This virgin aggregate is generally stockpiled until it is needed. It is often exposed to the atmosphere and to rain, snow, etc. The moisture content of virgin aggregate can vary, but it is often not insignificant. As a constituent of HMA, the virgin aggregate is necessarily heated far above the boiling point of water during the asphalt production process. This heating across the vaporization point (which also dries the virgin aggregate) consumes a large amount of energy. Much of the total energy supplied to a drum heater in an asphalt plant is consumed in heating and drying the constituents of HMA, including virgin aggregate material.
Consequently, there exists a need for improved methods and systems for cost effectively heating and drying virgin aggregate material used in asphalt production.